Merge ~sajoupa/charm-telegraf:tags_avoid_conflicts into charm-telegraf:master

[Laurent Sesquès]

tags: avoid conflicts if we set juju_*, with priority to the custom set ones

[Benjamin Allot (ballot)]

LGTM (small not blocking comment inline)

review: Approve

[Laurent Sesquès (sajoupa)]

Addressed Ben's comment (using an OrderedDict to get an identical output at each run).
Passed `make test`.

[🤖 Canonical IS Merge Bot (canonical-is-mergebot)]

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[🤖 Canonical IS Merge Bot (canonical-is-mergebot)]

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[Benjamin Allot (ballot)]

Ordereddict works to keep a consistent output but doesn't sort the tag in the configuration file.

I think sorting the tag increase the readability anyway but it's not a blocker indeed.

review: Approve

[🤖 Canonical IS Merge Bot (canonical-is-mergebot)]

Failed to merge change (unable to merge source repository due to conflicts), setting status to needs review.

[🤖 Canonical IS Merge Bot (canonical-is-mergebot)]

Change successfully merged at revision 4d2c141f6be61f11f16936468d68e8f8bb1e7703

diff --git a/src/reactive/telegraf.py b/src/reactive/telegraf.py
index 4c06424..99af5d8 100644
--- a/src/reactive/telegraf.py
+++ b/src/reactive/telegraf.py
@@ -16,6 +16,7 @@
 
 import base64
 import binascii
+import collections
 import hashlib
 import io
 import ipaddress
@@ -564,19 +565,25 @@ def configure_telegraf():  # noqa: C901
         except binascii.Error:
             # not bas64, probably already up to date configs
             pass
-    tags = []
 
-    if config["tags"]:
-        for tag in config["tags"].split(","):
-            key, value = tag.split("=")
-            tags.append('{} = "{}"'.format(key, value))
-    # add extra juju-related tags to be exposed as labels
-    tags.append('juju_application = "{}"'.format(get_remote_unit_name().split("/")[0]))
-    tags.append('juju_unit = "{}"'.format(get_remote_unit_name().replace("/", "-")))
+    tags = []
+    # Initialize juju-related tags to be exposed as labels
+    # Using a dict to avoid duplicates, which telegraf will see as conflicts
+    tags_dict = collections.OrderedDict()
+    tags_dict["juju_application"] = get_remote_unit_name().split("/")[0]
+    tags_dict["juju_unit"] = get_remote_unit_name().replace("/", "-")
     try:
-        tags.append('juju_model = "{}"'.format(hookenv.model_name()))
+        tags_dict["juju_model"] = hookenv.model_name()
     except KeyError:
         pass  # support older Juju 1.x deploys
+    # Parse juju-configured tags, which can override the 3 juju_* defined above
+    if config["tags"]:
+        for tag in config["tags"].split(","):
+            key, value = tag.split("=")
+            tags_dict[key] = value
+    # Render the tags dict into an array
+    for key, value in tags_dict.items():
+        tags.append('{} = "{}"'.format(key, value))
     context["tags"] = tags
 
     if inputs:
diff --git a/src/tests/unit/test_telegraf.py b/src/tests/unit/test_telegraf.py
index 1f9372f..128ede2 100644
--- a/src/tests/unit/test_telegraf.py
+++ b/src/tests/unit/test_telegraf.py
@@ -861,17 +861,18 @@ outputs:
 def test_default_tags_juju2(monkeypatch, config):
     monkeypatch.setattr(telegraf.hookenv, "principal_unit", lambda: "principal-unit")
     monkeypatch.setattr(telegraf.hookenv, "open_port", lambda p: None)
+    config["tags"] = "juju_model=custom-model-name,juju_application=custom-app-name"
     telegraf.configure_telegraf()
     expected = """
 [tags]
   # dc = "us-east-1" # will tag all metrics with dc=us-east-1
   # rack = "1a"
 
-  juju_application = "remote-unit"
+  juju_application = "custom-app-name"
 
   juju_unit = "remote-unit-0"
 
-  juju_model = "telegraf-test-model"
+  juju_model = "custom-model-name"
 
 """
     config_file = base_dir().join("telegraf.conf")